This invention reveals improvements in a flexible robotic limb which can function as a robotic snake, here called a robo-snake. These improvements are particularly pertinent to miniaturization applications such as catheters or positioners for microsurgery, micro-assembly, micro-manipulation, or micro-exploration. This invention features improvements in a prior-art flexible robotic arm of Rennex, U.S. Pat. No. 5,129,279, which issued in July, 1992. This prior-art invention incorporated the following basic structural features. The flexible arm comprised a series of expansible base units which were interconnected by six independently controlled length actuators. This interconnection was accomplished with universal joints. This structure was very versatile is terms of its motion. Each stage could extend, tilt, twist, and expand or contract radially. The combination of stages could position its working end along a tortuous path, and it could self-propel itself along a grid, a tunnel, or a blood vessel. It could also grip objects or position tools or imaging devices. Other features included optimal simplicity of control, ease of construction, lightness, and stiffness.
The most important element of the current invention in its two forms, a robo-snake or a flexible robotic arm, is the length actuators, especially for miniaturization. Inventor Rennex has submitted three patents for length actuators with the same application date as for the current invention. (These serial numbers will be provided.) All three of these attempt to minimize the actuator size. The first is titled "Inchworm Actuator"; it provides for improvements over the prior art of inchworm linear motors to achieve miniature actuators. The second is titled "Micro-Actuator"; it provides for a two-way, micro-machined actuator which can be internally locked at a particular length. The third is titled "Free-Standing Traveling-Wave Actuator"; it provides for a traveling-wave ultrasonic motor of minimal size which can be free-standing as required in the robo-snake. All of these actuators can be configured in such a way that they are "free-wheeling" when the power is cut off, which may be an advantage in terms of safety.